1. Field of the Invention
The present invention relates to digital automatic gain controllers (AGC) of the type that may be programmed by a microprocessor (uP) or a remote controller. More particularly, the present invention relates to a novel automatic digital gain controller for digital communication receivers. A feature of the automatic gain controller is to provide very fast recovery from interference and jamming signals which would saturate the analog to digital converters which in turn would substantially decrease the sensitivity of the receiver.
2. Description of the Prior Art
Heretofore, digital communication receivers and spread spectrum communication systems of the type adapted to be immune to interception and jamming have been proposed. Such proposed systems have various types of encoding and decoding apparatus and modulation codes.
A proposed programmable anti-jam Modem is generally described in a report entitled "Design Plan (Draft) VHSIC AJ Modem" U.S. Government Contract DAAK-20-83-G-0454 dated Jul. 30, 1984 by Hughes Aircraft Company Communication System Division in Fullerton, Calif. This proposed modem does not teach or suggest an all digital gain controller or the problems introduced by jamming signals which drive the receiver data signals into saturation so that the desired data signals cannot be easily recovered.
The problem generated by burst jamming signals in communications receivers is discussed in U.S. Pat. No. 4,890,297 issued Dec. 26, 1989, and entitled Burst Jammer Erasure Circuits for Spread Spectrum Receivers. This patent was issued to Unisys Corporation, the assignee of the present application, and is directed to a solution using analog devices in the recovery loop.
It would be desirable to provide a novel digital gain controller that is cheaper and simpler than prior art gain controllers adapted to operate in hostile signal noise and jamming environments.